1. Field of the Invention
The present invention relates generally to fire detection and more specifically to fire detection in tunnels using a linear heat sensor.
2. Background of the Invention
Fire detection systems are required to detect fires in a multitude of places. Fire detection systems have been developed for use in the home, in office buildings, and in tunnels. One such tunnel fire detection system is sold under the name xe2x80x9cFibroLaserxe2x80x9d by Siemens Building Technologies AG, Cerberus Division, formerly Cerberus AG (hereinafter xe2x80x9cthe FibroLaser Systemxe2x80x9d). The FibroLaser System includes a glass-fiber cable, a laser light source, a wave guide, and an optoelectronic receiver. The glass-fiber cable is made of silica glass and should be installed along a tunnel roof. The laser is placed in registration with one end of the glass-fiber cable and the wave guide is placed in registration with the other end of the glass-fiber cable. Light generated by the laser is conveyed in a longitudinal direction along the glass-fiber cable. Variations in the density of the silica glass caused by heat give rise to a continuous scattering of the laser light being transmitted therein, otherwise known as Rayleigh scattering, which in turn gives rise to attenuation of the laser light. In addition, thermal lattice vibrations of the silica glass lead to further light scattering known as Raman scattering.
The scattered light propagates along the glass-fiber cable and enters the wave guide. A fraction of the scattered light falls into an acceptance angle of the wave guide which causes it to scatter both in a forward and backward direction. Some of the scattered light is detected by the optoelectronic receiver. The optoelectric receiver evaluates the intensity of specific backscatter frequencies, which allows the optoelectric receiver to determine the local glass-fiber temperature. The local resolution of the temperature profile along the glass-fiber cable is determined by measuring the subduing of the wave guide light. The magnitude of the fire is a function of the heated cable length: a short heated length corresponds to a small fire and a long heated length corresponds to a large fire. An alarm can be set which is triggered by the magnitude of the fire.
Because of the complex thermodynamic processes which occur during a fire, it is virtually impossible for all of the influencing quantities which occur during the fire to be fully taken into account. Therefore, configuring a detection system including a linear heat sensor is extremely laborious and time-consuming and entails numerous practical trials. Clearly, there exists the need to simplify this process.
The present invention relates to a method of configuring a tunnel fire detection system comprising a linear heat sensor. The method according to the invention is to enable tunnel fire detection systems to be individually adjustable as early as during the planning stage in a highly flexible manner subject to the physical and local conditions of a tunnel.
The stated object is achieved according to the invention on the basis of parameters of the tunnel and sensor cable as well as on the basis of fire models the fire development can be determined. And based on this fire development, fire alarm times, installation points for the sensor cable, and alarm limit values of the detection system can be calculated and optimized in such a way that a potential fire is quickly and reliably detected.
In a preferred embodiment the system for configuring a tunnel fire detection system comprising a linear heat sensor includes a storage device, a plurality of parameters, a plurality of partial fire models, an input device, a processing unit and an output device. The storage device stores the plurality of parameters and the plurality of partial fire models. The plurality of parameters include a plurality of tunnel parameters describing the tunnel, and a plurality of sensor parameters describing the linear heat sensor. The plurality of partial fire models describing aspects of fire development. The input device allows for entering the data and parameters into the system. The processing unit calculates the fire development and the resultant heating of the sensor cable on the basis of the plurality of parameters and the plurality of partial fire models. The display device outputs the alarm limit values and fire alarm times, which are obtained based upon the plurality of parameters and the plurality of partial fire models.